The concept of realizing electronic applications on flexible, particularly elastically stretchable, ‘skins’ that conform to irregularly-shaped surfaces is revolutionizing fundamental research into mechanics and materials that can enable high performance stretchable and flexible electronic devices. Such stretchable and flexible electronic devices are expected to find wide application in the field of wearable electronic devices, and the like. It is widely believed that the ability to operate such stretchable and flexible electronic devices under various mechanically-stressed states will provide a set of unique functionalities that are beyond the capabilities of conventional rigid electronics.
Owing to rapid development in recent years, some mechanically deformable devices have been demonstrated to operate almost at par with their rigid counterparts in consumer applications such as organic LEDs,[1] stretchable displays,[2,3] and high-speed transistors,[4] as well as devices operating on the epidermis.[5] However, the wide reach of this technology is still yet to be fully exploited.
For instance, flexible sensors capable of sensing chemical or biological substances, particularly gases, would be useful in the event a person has to venture into a potentially hazardous environment. However, the realization of a flexible gas sensor that can operate at room temperature to enable the detection of a gas at low concentration is still very much in its infancy.[6] Indeed, most gas sensors, even on rigid platforms, are required to operate at elevated temperatures of several hundred degrees Celsius.[7]
In the case of imaging systems for sensing electromagnetic radiation, particularly ultra-violet (UV) radiation, these systems are typically fabricated on rigid planar substrates on account of the demanding requirements on the detectors in terms of high dynamic range, low noise, high speed, and high resolution, and the limitations associated with the optical elements used in such imaging systems. However, when comparing such planar electronic imaging devices such as CMOS sensors to biological imaging systems such as the human eye, these rigid imaging sensors invariably lack the performance, especially when comparing field of view and aberrations,[8] due to their inherent flat design.[9]
It is widely believed that by curving the plane of the sensing element so as to mimic the human eye, this would reduce the distortion and chromatic aberration significantly, thereby improving the performance of such imaging systems. This would be especially important for imaging at non-visible wavelengths such as the UV A and B regime, due to the low availability and high cost of suitable optics. In this respect, readily available, low complexity devices with flexible characteristics would be favourable for applications such as imaging of visible-blind UV radiation for monitoring of sterilisation, lithography, flame detection, environmental studies and military applications.[1]
While there is a significant need for flexible sensors capable of detecting substances and/or electromagnetic radiation with sufficient sensitivity to be effective in the field of say, wearable electronic devices, there are clearly limitations that present a significant barrier to the realisation of such flexible sensors.
The present invention seeks to provide a flexible or stretchable sensor for use in detecting a substance and/or electromagnetic radiation and a method for the detection thereof, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.